Fiber blade with leading edge reinforcement

ABSTRACT

This invention concerns a leading edge reinforcement for a fiber reinforced blade suitable for use in a gas turbine engine. The reinforcement comprises two strips of metal joined together at and adjacent to an edge which is shaped to form the leading edge of the blade. At least a part of the remaining portion of the metal strip serves for the attachment of the reinforcement to the blade.

Waite Gwin 14 1 Sept. 11, 1973 I54] FIBER BLADE WITH LEADHNG EDGEREHNFORCEMENT [56] References Cited [75] Inventor: John R. Goodwin,Ockbrook, UNITED STATES PATENTS Engmd 3,176,775 4/1965 Clemens 416/23073 Assignee; The secretary f state f D f 3,294,366 12/1966 Coplin416/224 London, England Primary ExaminerL. Dewayne Rutledge 4 51mmemi"':M.-. nq cw PP 250,744 AYtorney-Cushman, Darky & Cushman and LloydRelated us. Application Data Street [63] Continuation of Ser. No.867,653, Oct. 20, 1969,

abandoned. I 57] ABSTRACT [30] Foreign Application Priority Data Thisinvention concerns a leading edge reinforcement Oct 22 1968 GreatBritain 50 058/68 for a fiber reinforced blade suitable for use in a gasturbine engine. The reinforcement comprises two strips of 2 metal joinedtogether at and adjacent to an edge wh1ch 2 fi 8 416/230 g6 g ii isshaped to form the leading edge of the blade. At least a p of theremaining portion of the metal Strip serves [58] Fleld of Search416/224, 229, 230, for the attachment of the reinforcement to the blade3 Claims, 4 Drawing Figures PATENTEDSEPI 1 ma SHEET 1 BF 2 Inventor 9 W2 y PAIENIEB EPH H 3,75 ,234

SHEET 2 [IF 2 Z By M ztorney I FIBER BLADE WITII LEADING EDGEREINFORCEMENT This application is a continuation of my earlierapplication, Ser. No. 867,653, filed Oct. 20, 1969 and now abandoned.

This invention relates to a blade reinforcement and is particularlyconcerned with a reinforcement for a blade of a gas turbine engine.

According to the present invention a leading edge reinforcement for theaerofoil section of a fibre reinforced blade or vane comprises twosheets or strips of metal joined together at and adjacent an edge whichis shaped to form the leading edge of the blade, the portion of thestrips or sheets opposite said edge serving for attachment of thereinforcements to said aerofoil section.

Preferably said sheets are joined together over a strip of surfaceextending parallel to and including said leading edge.

Said joint may be a seam weld, an electron beam weld or a brazed jointor a glued joint.

Said remaining portion of the strips may be of thinner section than theleading edge portion of the strips.

According to another aspect of the invention a method of manufacturingthe leading edge reinforcement for a fibre reinforced blade comprisesthe steps of cutting two sheets of metal to form strips having a desiredleading edge'curve, if necessary machining the portions of the stripsdistant from the leading edge to facilitate attachment thereof to ablade, joining the strips together at and adjacent the leading edge, andmachining the leading edge portion of the strips to form the desiredportion of the aerodynamic profile of the blade.

Said machining preferably comprises chemical machining.

According to a further aspect of the invention a method of manufacturinga blade comprises the steps of manufacturing a leading edgereinforcement according to the preceding paragraphs, laying up sheets offibre reinforced material to form a blade core, trapping said blade corebetween said strips, and further laying up sheets of fibre reinforcedmaterial on the outside of said strips to form the remainder of theblade.

The invention also comprises a blade having a leading edge reinforcementaccording to the preceding paragraphs.

The .invention will now be particularly described merely by way ofexample with reference to the accompanying drawings in which FIG. 1 is apartly broken away elevation of a gas turbine engine incorporatingblades having reinforcements according to the invention,

FIG. 2 is an enlarged section of the leading edge of a blade of theengine of FIG. 1 and according to the invention,

FIG. 3 shows a method of assembing a reinforcement according to theinvention, and

FIG. 4 is a view similar to FIG. 2 but of a further embodiment.

Referring first to FIG. 1, a gas turbine engine is generally indicatedat and comprises a compressor section ill, a combustion section 12, aturbine section 13 and a final nozzle 14 all in flow series. The casingof the engine is broken away at the forward end of the compressorsection II to show a first stage of rotor blades 15 and a first stage ofstator blades 16.

It will be appreciated that since the rotor blades 15 are the firstobstruction which is met by air sucked into the engine, they will alsobe prone to damage by bird and other foreign object ingestion. In theinterests of lightness the blades may be made of fibre reinforcedcomposite material; in this case they may be relatively easily damagedby foreign body ingestion. They are therefore provided with a leadingedge reinforcement which can be seen at 17 in FIG. 1 and which is moreeasily visible from FIG. 2 which is a section on one of the blades 15showing only the leading edge portion.

' The leading edge reinforcement 17 comprises two strips of metal 18 and19 which are joined together at 20 at and adjacent the leading edge 21.

The remaining portion of the strips 18 and 19 is formed to produce athinner section as can be seen at 22 and 23. The thin sections 22 and 23are interlaminated with the laminations generally indicated at 24 whichin this particular instance comprises layers of carbon fibre reinforcedresin with which are interposed some layers of steel.

It will therefore be seen that the leading edge reinforcement 17provides a rigid metal leading edge for the blade which is stronglyattached to the composite material forming the remainder of the aerofoilsection of the blade. Further detail of the construction is explainedmore fully below with reference to the method of manufacturing andassembling the reinforcement and blade.

To manufacture the reinforcement 17 a pair of sheets of metal, which maybe of substantially rectangular shape as shown at 25 in FIG. 3, are cutadjacent one edge to form a shape corresponding to the curve of theleading edge of the desired blade shape. This curve is shown at 26 onthe sheet 25 of FIG. 3. The portions 22 and 23 of the sheets are thenmachined so as to reduce their thickness; chemical machining ispreferably used. These two sheets are then laid one on top of the otherso that their leading edges correspond, and a strip adjacent the leadingedge welded, brazed or glued together. This joining strip is shownhatched at 27. It should be noted that although electron beam weldingcould be used to join the pieces, we in fact prefer to use seam welding,the beam being directed between the sheets and caused to oscillate so asto produce a reasonable section of welding.

The joined sheets are then pressed or otherwise formed to correspond tothe twist and camber of the required blade section (it should be notedthat it would be possible to effect this forming operation before thesheets are joined together). The reinforcement thus formed has a leadingedge which is of rectangular cross-section as in fact is shown in chainlines at 28 in FIG. 2, and the portions of thesheets distant from theleading edge are of thesame thickness as the portions at the leadingedge. The reinforcement isnext machined to taper the leading edgeportion and to round off the leading edge itself.

To assemble the reinforcement 17 to the blade the following technique isused. A blade core is manufactured by the laying up of laminations offibre reinforced material, and if desired interlaminations of steel ortitanium sheets may be included. This core is shown at 28 in FIG. 2. Thereinforcement 17 is then pushed on to the core 28 so that the portions22 and 23 trap the core between themselves. It may be desirable toseparate the portions 22 and 23 in the forming operation; otherwise thenip between the portions 22 and 23 may be used to hold the reinforcementon the core 28.

Further laminations of the fibre reinforced material are then laid up onthe assembled reinforcement and core until the laminations match up withthe core leading edge as can be seen at 29. The completed blade andreinforcement may then be cured and if necessary an anti-erosion coatingmay be applied to those areas where the fibre reinforced material formsthe external surface of the blade.

FIG. 4 shows a second embodiment. In this case the reinforcement 30 ismade by cutting two sheets as in the FIG. 2 embodiment, forming thesheets to the desired blade camber and twist, and chemically eroding theportions of the sheets distant from the leading edge so as to thin thisportion out in a series of steps as shown at 31. The sheets are thenplaced together and seam welded along the leading edge to form a weldslug as shown at 32. The leading edge is next machined from the formshown in chain-lines in FIG. 4 to its final aerodynamic shape.

The reinforcement 30 is again assembled to the blade core 33 and thecomplete blade is cured, but in this case the reinforcement extendsalong both flanks of the blade forming at least part of the surfacethereof. In fact the portion lying on the pressure side of the blade mayextend to the trailing edge of the blade.

It will be appreciated that this latter construction provides somefurther advantages. The stepped portions 31 form a good key forattachment of the fibre reinforced material to the reinforcement, andthe steps may be chosen to be of thickness equal to that of thelaminations of the fibre reinforced material to ensure good matching ofthe core and the reinforcement. The portions of the reinforcement forman anti-erosion coating for the blade, and additionally thereinforcement forms a torsional stiffener for the blade itself by virtueof its cross-sectional shape.

It will be appreciated that a number of modifications can be made to theabove embodiment. Thus a number of materials are suitable for themanufacture of the leading edge reinforcement 17 although we prefersteel or titanium. Again the sequence of machining operations issusceptible to re-arrangement; thus it would be possible to form thesheets before or after welding and one could crop the sheets eitherbefore or after the sheets are joined together. Although chemicalmachining is preferred for the shaping of the reinforcement sheets, itwould of course be possible to use electro chemical machining or evenconventional metal re moval techniques.

What we claim is:

1. In combination with a fiber reinforced gas turbine blade having aleading edge, a fiber aerofoil section and a trailing edge, an edgereinforcement for reinforcing the leading upstream edge of said fiberreinforced gas turbine blade, said reinforcement comprising:

first'and second strips of metal, each strip having a first section witha first thickness and a second section with a second thickness thinnerthan said first thickness,

said first and second strips being joined along at least a portion ofsaid first sections adjacent the leading edge of said blade, and

said second thinner sections of said first and second strips extendinginto the fiber aerofoil section for strongly attaching said stripsthereto.

2. The combination of claim 1, wherein the first section of said firstand second strips are joined together forming the outer surface of theleading edge of said blade.

3. The combination of claim 1, in which fiber reinforced material isprovided on the outside of said blade, covering at least a portion ofsaid thinner sections of said first and second strips.

1. In combination with a fiber reinforced gas turbine blade having a leading edge, a fiber aerofoil section and a trailing edge, an edge reinforcement for reinforcing the leading upstream edge of said fiber reinforced gas turbine blade, said reinforcement comprising: first and second strips of metal, each strip having a first section with a first thickness and a second section with a second thickness thinner than said first thickness, said first and second strips being joined along at least a portion of said first sections adjacent the leading edge of said blade, and said second thinner sections of said first and second strips extending into the fiber aerofoil section for strongly attaching said strips thereto.
 2. The combination of claim 1, wherein the first section of said first and second strips are joined together forming the outer surface of the leading edge of said blade.
 3. The combination of claim 1, in which fiber reinforced material is provided on the outside of said blade, covering at least a portion of said thinner sections of said first and second strips. 